The restructuring is a response to a shift by customers away from premium package-delivery services and toward slower, less expensive modes as the global economy struggles to grow.

Employees who volunteer for the program will receive four weeks of pay for every year of service, capped at two full years of base pay. FedEx has said previously that the buyouts should reduce ‘‘fixed headcount by several thousand people.’’

Those eligible will be notified in February and have until­ April to apply. They will find out in May if they have been accepted.

The first wave of employees will leave on May 31, the last day of FedEx’s fiscal year.

Founder and CEO Fred Smith said in August that most of the cuts will come in the company’s Express and Services units, which have been hurt the most by global economic conditions.